I know this may sound pretentious, but producing a deep mirror finish on a black car and keeping it that way without swirl marks or impurities takes time, discipline and resources. I remember when I first purchased my 2001 E39 530i it took me around 42 hours to bring it up to the standard I was happy with. The interior was relatively simple, using fine leather polishes and a shit-load of carpet shampoo. The exterior was another story.... Which involved mixing up my own secret citric wash to remove every single alien particle on the car, and then doing it again and again inside a freestanding clean room built in an enclosed garage. Then cutting the clear coat down with electric buffers aided by high powered lighting, before building up and layering soft Carnubra based waxes up over several days; and finally sealing it all in with an outer synthetic shell of durable wax. Then repairing all of the plastics, both on the body and inside the engine bay. The finished product was just ridiculous, would have put show cars to shame. But keeping it that way was the hard part, washing needed to be done a certain way with certain types of materials in order to avoid removing the synthetics; and the synthetic wax reapplied like clockwork so that the Carnubra never came in contact with the elements. After about a year, I just gave up on the whole deal. It was just too much work.
When the modifications to the FX50s are complete, i'll likely try to observe these same principals again. Because i'm a perfectionist at heart. But not to the same extent.
I'll try to find some pictures of a couple cars I restored for friends whilst I was in the Defense Force, one was a Black Ute and the other was a Skyline, came out looking like black mirrors.